<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Document</title>
</head>
<style>
.box1{
    width: 200px;
    height: 200px;
    /* background-image: linear-gradient(to right,red,yellow,blue,black); */
    background-image: radial-gradient(red ,yellow);
}
/* to left
    to right 
    to top
    to bottom
    deg表示度数
    turn表示圈 
    线性渐变： radial-gradient*/
</style>
<body>
    <div class="box1"></div>
</body>
</html>